Linear actuators are widely used to operate mechanical devices, especially in the aircraft, aerospace, and automotive fields. Rack-and-pinion and worm gears driven by electric motors are common examples. Hydraulic piston/cylinder assemblies are another common example.
Such actuators are widely used despite their disadvantages. The electrically driven units require relatively heavy motors whose rotary output must be converted to linear motion, again by heavy mechanisms. In airborne or space applications, such extra weight is a serious penalty.
Hydraulically or pneumatically driven actuators require hydraulic or air lines which can be cut or might otherwise leak past the seals which are necessary for the assembly of the system. Further, sliding seals are required in the actuators themselves, and these involve friction losses, requiring overdesign of the system to assure an adequate force output, as well as the risk of leakage. These devices require an external power-fluid supply, which itself is bulky and subject to malfunction.
The reduction of friction enabled by the transmission of this invention is very important when the actuating force is derived from a relatively weak source such as an electromagnetic solenoid.
It is an object of this invention to provide a force-amplifying linear actuator which, while it includes a transmission, is self contained and independent of external fluid supplies. It can be powered by a simple plunger. Because of the capsular construction of the transmission, it requires no static or sliding seals, and therefore operates with minimal friction losses.
It is another object of this invention to provide an actuator whose energy is supplied merely by electrical conductors, which can be provided with redundant systems, and which can provide a linear output from a non-linear electromagnetic supply without need for rotary-to-linear conversion means, or a non-linear output from a linear input.
It is another object of this invention to provide a linear actuator whose rate of extension and force can be "tailored" to suit an intended installation, simulating the effect of a cam device.